Advancements in semiconductor technology have led to the production of large scale integrated circuits which have revolutionized the electronics industry. Microelectronic components are now widely used in the production of a variety of electronic devices, such as portable computers, calculators, watches, cordless telephones, radios, tape recorders, and security systems. Development of such electronic devices has brought about the evolution of batteries as miniature power supplies. In light of their applications, this new generation of batteries must produce higher energy per unit volume and superior discharge characteristics.
The technology related to thin solid state batteries has been developing at a rapid pace. Thin solid state batteries are typically fabricated employing an alkali metal anode, a non-aqueous electrolyte, and cathodes of nonstoichiometric compounds, such as teachings of U.S. Pat. Nos. 4,621,035; 4,888,206; 4,911,995; 5,169,446 and 5,080,932. Of the alkali metals commercially feasible in manufacturing the anode material, lithium is preferred because it has a low atomic weight, while having a high electronegativity. These thin batteries require a high energy density, a long shelf life and efficient operation over a wide range of temperatures.
One known method for fabricating a thin battery cell is shown in FIGS. 1 (A-G). Referring to FIG. 1(A), a current collector film 110 is initially provided. Collector film 110 can comprise a variety of conductive materials, including but not limited to stainless steel, copper, nickel or aluminum. Subsequently, as shown in FIG. 1(B), a cathode layer 112 is positioned superjacent the current collector film, preferably by extrusion. This step also involves curing to sufficiently polymerize the cathode. Referring to FIG. 1(C), after the cathode layer is cured, an electrolyte layer 114 is positioned superjacent the cathode and subsequently cured, thereby forming current collector-cathode-electrolyte sandwich 115. Next, from the current collector-cathode-electrolyte sandwich 115, a multitude of subsections 116 are formed, as shown in FIG. 1(D). Then, each subsection 116 has an anode foil 118 comprising lithium or some other suitable alkali positioned superjacent, as illustrated in FIG. 1(E). Referring to FIG. 1(F), a second conductive layer 120 is then subsequently positioned superjacent the anode foil 118.
Referring to FIG. 1(G), each subsection 116 is then packaged in a stainless steel enclosure 122 such that one current collector is in electrical contact with the top portion 124 of the stainless steel enclosure and the other collector is in contact with the bottom portion 126 of the enclosure. To ensure against potential shorting, insulation 128 is positioned within the enclosure between the top and bottom portions of the stainless steel enclosure.
Previously, thin battery manufacturing technology has relied on forming and assembling the anode, electrolyte, and cathode of the battery as separate components. However, this is a relatively labor intensive procedure that involves the intricate assembly of a number of discrete components. The stamping and handling of individual discs of lithium is particularly costly and awkward because of lithium's expense and relatively high reactivity. Thin lithium foil is also difficult to work with. Thin lithium foil comprises malleable, low tensile strength properties. Moreover, lithium foil adheres to a large number of other materials.
In light of these shortcomings, there have been several developments in the manufacturing processes of thin battery technology. These advancements, such as U.S. Pat. No. 4,911,995, and U.S. Pat. No. 4,621,035, have relied on the utilization of a thin metal film as a metalization layer. This metalization layer is then employed with an alkali metal to form an anode. However, these approaches fail to provide a battery which has the flexibility and durability required in some electronics applications, as well as a simplified means for manufacturing.
Polymer thick film inks have yet to be examined as a conductive layer from which a lithium anode may be formed. Many of the difficulties in manufacturing polymer batteries are related to handling and assembling the lithium anodes, the cathodic polymers and the electrolytic polymers. These issues are compounded in part because most techniques known in the art for fabricating these battery types involve forming one battery cell at a time .